VLAN 20 with Protocol as AppleTalk. Select and enable Port 3, Port 4
and Port 5 for Protocol VLAN feature.
7.7 VLAN VPN
With the increasing application of the Internet, the VPN (Virtual Private Network) technology is
developed and used to establish the private network through the operators’ backbone networks.
VLAN-VPN (Virtual Private Network) function, the implement of a simple and flexible Layer 2 VPN
technology, allows the packets with VLAN tags of private networks to be encapsulated with VLAN
tags of public networks at the network access terminal of the Internet Service Provider. And these
packets will be transmitted with double-tag across the public networks.
The VLAN-VPN function provides you with the following benefits:
(1) Provides simple Layer 2 VPN solutions for small-sized LANs or intranets.
(2) Saves public network VLAN ID resource.
(3) You can have VLAN IDs of your own, which is independent of public network VLAN IDs.
(4) When the network of the Internet Service Provider is upgraded, the user’s network with a
relative independence can still work normally without changing the current
configurations.
In addition, the switch supports the feature to adjust the TPID Values of VLAN VPN Packets. TPID
(Tag Protocol Identifier) is a field of the VLAN tag. IEEE 802.1Q specifies the value of TPID to be
0x8100. This switch adopts the default value of TPID (0x8100) defined by the protocol. Other
manufacturers use other TPID values (such as 0x9100 or 0x9200) in the outer tags of VLAN-VPN
packets. To be compatible with devices coming from other manufacturers, this switch can adjust
the TPID values of VLAN-VPN packets globally. You can configure TPID values by yourself. When
a port receives a packet, this port will replace the TPID value in the outer VLAN tag of this packet
with the user-defined value and then send the packet again. Thus, the VLAN-VPN packets sent to
the public network can be recognized by devices of other manufacturers.
The position of the TPID field in an Ethernet packet is the same as the position of the protocol type
field in the packet without VLAN Tag. Thus, to avoid confusion happening when the switch
forwards or receives a packet, you must not configure the following protocol type values listed in
the following table as the TPID value.
Protocol type Value
ARP 0x0806
IP 0x0800
MPLS 0x8847/0x8848
IPX 0x8137
IS-IS 0x8000
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